NOAA NWS - Iceland Weather - US government site provides hour-by-hour weather conditions for the past 24 hours for major cities and locations in the country.
BBC Weather Centre - Country Guides: Iceland - Provides climate and weather information, facts and statistics about the country, along with five-day forecasts for major cities.
Weather Underground - Iceland - Displays current conditions for all major cities on one page, with five-day forecast and more detailed information for each available.